Acetylcholine Receptor Ab (ACRA)
Laboratory offering test
Also known as/Frequency of test
ACR; ACHR; Myasthenia antibody; Motor end plate antibody; MG antibody, ACRA
Acetylcholine receptor antibodies are a highly sensitive and specific marker for generalised myasthenia gravis (80-90% sensitivity); up to 90% of generalised MG cases are ACHR positive for ACHR antibodies whilst in pure ocular MG up to 50% of patients are positive Level of antibodies do not correlate with disease activity, so repeated testing is not indicated. In patients with suspected MG who are negative for ACRA, anti-MuSK (muscle-specific receptor tyrosine kinase) antibodies may be indicated.
Plasma NOT acceptable. Referred outside of EPA
Turnaround times (TAT) Urgent/Routine/GP or OPD
<0.2nmol/L Negative 0.2 – 0.4 nmol/L Doubtful >0.4nmol/L Positive